Weighing a moving object using captured torque data

ABSTRACT

Methods and apparatus for weighing an article, such as a mail piece, while the article is moving at high speed. An article ( 900 ) is received from an intake transport ( 1200 ), and gripped in a weighing station ( 1310 ), in between a capstan roller and a pinch roller ( 1316 ), which are synchronized to minimize slipping. A first precision servo system ( 1252, 1250 ) alters the speed of the article, and in the process acquires torque data for storage and analysis ( 1212, 1282 ). A second precision servo system ( 1260, 1330 ) applies a constant force, via a tension arm ( 1320 ), urging the pinch roller ( 1316 ) against the capstan roller, independently of the thickness of the mail piece. Fourier analysis can conveniently be applied for analyzing the acquired current data and comparing to stored calibration data to determine weight. Weight is determined without regard to the actual speed of the moving article.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/855,130 filed Sep. 13, 2007, now U.S. Pat. No. 7,687,727 issued Mar.30, 2010, incorporated herein by this reference. This case also claimspriority from U.S. Provisional Application No. 61/101,995 filed Oct. 1,2008 and incorporated herein in its entirety by this reference.

TECHNICAL FIELD

This invention pertains to methods and apparatus for accuratelydetermining mass-related properties of an article, such as weight ormoment of inertia, and more specifically it pertains to weighingarticles that are in motion. In the case of mail pieces, another featureis ensuring that proper postage is paid.

BACKGROUND OF THE INVENTION

Many weighing systems are known, some dating back to biblical times.More recently, weighing systems have been developed for weighing eachone of a stream of articles, such as mail pieces or parcels movingthrough a transport or mail sorting system. Prior art systems of thattype are shown, for example, in U.S. Pat. Nos. 7,096,152 and 3,648,839.

Some known systems rely on back-EMF or “Electro Magnetic ForceRestoration” principles. According to one vendor, “an applied load iscompensated for by an electromagnetically produced counterforce. Aprecision position control (optical) keeps the system stable. Theslightest movement is detected, initiates a feedback circuit to runcurrent through a coil and causes the load to be returned to itsoriginal position. The coil current, which is proportional to theweight, is transmitted to an internal A/D converter then processed inthe microprocessor.”

The need remains for improvements in accuracy, speed (throughput),reduced cost, and reducing the need for frequent re-calibration ofweighing systems. The present application achieves these and other goalsby applying a dramatically different approach to the problem as furtherexplained below.

Postal services typically charge for delivery of mail pieces by theirweight, among other criteria. In general, the heavier the mail piece,the more is charged. Bulk mailers, who may mail thousands of pieces at atime, sometimes intermix heavier mail pieces with lighter ones, and putthe postage appropriate for the lighter pieces on every piece. This canoccur, for example, when a bank mails out its customer statements. Moststatements contain a few sheets and easily fit under the one ouncecut-off, but some of them contain many sheets and are overweight. Veryoften the banks do not put proper postage on the heavier pieces.

Audits, sometimes run by manually weighing suspect mail pieces, indicatethat the US Postal Service loses many millions of dollars each yearbecause of this practice. Because current methods of weighing mailpieces are either too slow for existing sorting machines or requireindividual or a set of mail pieces to be weighed manually, postalservices have not devised methods for ensuring proper postage on eachmail piece. It is important to remember that postage applies to eachmail piece, not to the average weight within a set of mail pieces. As aresult, a set of mail pieces whose average weight is under the limit maystill contain many mail pieces that are individually too heavy andrequire greater postage.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed to determiningmass-related properties of articles “on the fly,” i.e., as they movethrough a transport mechanism, by measuring an applied impulse requiredto move the article from one state to another. For example, an impulsecan be applied to accelerate an article from a first velocity to asecond (greater) velocity. That “impulse” can be applied through variouselectromechanical contrivances such as a motor. The magnitude of theimpulse can be measured in various ways. In one embodiment, an impulseis measured indirectly by monitoring the torque applied through a servomotor to accelerate the article. In the detailed description below, wediscuss mainly “weighing” of articles, but other embodiments andapplications within the scope of the present disclosure can be arrangedto measure mass-related article properties such as moment of inertia aswell. Further, much of what follows discusses a straight-line movementof the article, but a rotational or other system of movement is alsowithin the purview of the present disclosure.

In one class of embodiments, an article whose mass-related property isto be measured is presented, for example by entering a “weighingstation” via a transport mechanism such as a belt transport. Details ofsuch transport mechanisms are well known in various contexts, includingmail sorting machines. In alternative embodiments, the weighingapparatus might be used separately, for example in a machine arranged toapply the correct postage to a mail piece. In still other applications,the weighing apparatus may be used to provide rapid, accurate weighingof articles or materials, such as chemicals, pharmaceuticals or othersubstances unrelated to postal services. The concept of the presentinvention is applicable over a wide spectrum of applications.

In general, a weighing apparatus in accordance with the presentdisclosure receives an article that has a measured or otherwise knowninitial state of movement (or rest). There is also a predetermined or“commanded” final state of movement (or rest) of the article. Andfinally, a mechanism is provided that applies an impulse to move theobject from its initial state to the commanded final state. (The term“mechanism” is used in this application in a broad sense. It is notlimited to purely mechanical contrivances; to the contrary, it refers toany and all mechanical, electrical, optical, electromechanical systems,software controlled systems, and combinations thereof that provide thedescribed functionality.)

The impulse-applying mechanism must include or be coupled to some meansof measuring or capturing information as a proxy for the actual impulse.In other words, the impulse typically is measured indirectly. Forexample, a curve of the torque that applies the impulse through a motorcan be used to infer sufficient information about the applied impulse.The measured proxy is then calibrated by articles of known mass-relatedproperties and the calibrated values are used to determine the article'smass-related properties. The use of calibration is an important part ofthe system because it allows considerable simplification to take place.As explained below, in a preferred embodiment, this approach obviatesthe need for actual or absolute measurements such as article velocity.Indeed, velocity is not critical and need not be measured in absoluteterms. One primary improvement of the present invention over prior artis that it allows weighing of articles at normal transport speeds; forexample, hundreds of inches per second for mail pieces.

Another aspect of the present invention comprises a system for measuringthe weight of each mail piece in a stream of mail pieces, determiningthe proper postage for that mail piece, determining the amount ofpostage paid by the mailer, and segregating out mail pieces withimproper postage. The proper amount of postage may be based on the mailpiece's weight, size, thickness, mailing point, delivery point, or otherproperty, alone or in combination. Another aspect of the inventioncomprises a method for ensuring that proper postage has been paid foreach mail piece.

Additional aspects and advantages of this invention will be apparentfrom the following detailed description of preferred embodiments, whichproceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified electrical schematic diagram illustrating oneembodiment of a system for weighing articles on the fly.

FIG. 2 is a mechanical drawing in top view of an article transportapparatus including a weigh station in accordance with one embodiment ofthe present invention.

FIG. 3 is a mechanical drawing in top view showing greater detail of theweigh station of FIG. 2.

FIG. 4A comprises top view and cross-sectional views of an adjustablepinch roller assembly for use in the transport apparatus of FIG. 2.

FIG. 4B is a cross-sectional side view of a pivot roller assembly of atype useful in the weigh station of FIG. 2.

FIG. 4C is a side view of a pancake motor mounting in the articletransport apparatus of FIG. 2.

FIGS. 5-6 are mechanical drawings in top view illustrating a procedurefor replacing a pancake motor with a precision servo motor in theassembly of FIG. 2.

FIG. 7 is a side view illustrating a precision servo motor installedbelow a transport deck of a transport assembly with a sleeved hubinstalled for engaging an article moving through the transport assembly.

FIGS. 8A and 8B are oscilloscope traces of servo motor torquemeasurements taken in a development prototype weighing system inaccordance with one aspect of the present invention.

FIG. 9A is a top plan view of a transport assembly of a secondembodiment of an in-line weighing apparatus in a non-weighing state.

FIG. 9B is a top plan view of the transport assembly of FIG. 9A in aweighing state.

FIG. 10A is an exploded, perspective view of the transport assembly ofFIG. 9A.

FIG. 10B is an assembled, perspective view of the transport assembly ofFIG. 9A.

FIG. 11A is a top plan view of a transport assembly of a thirdembodiment of an in-line weighing apparatus in a non-weighing state.

FIG. 11B is a top plan view the a transport assembly of FIG. 11A in aweighing state.

FIG. 11C is an exploded, perspective view of the transport assembly ofFIG. 11A.

FIG. 11D is an assembled, perspective view of the transport assembly ofFIG. 11A.

FIG. 12 is a simplified electronic system diagram of a dual-servocontrolled in-line weighing apparatus in the context of a mail sortingsystem.

FIG. 13 is a side view of an embodiment of a dual-servo in-line weighingapparatus.

FIG. 14 is a top plan view the weighing apparatus of FIG. 13.

FIG. 15 is an enlarged top view taken along line 15-15 of FIG. 13showing drive linkage detail of the weighing assembly of the weighingapparatus of FIG. 13.

FIG. 16 is a perspective view of the weighing assembly with the deckshown in phantom.

FIG. 17 is a perspective view of a tension arm standing alone.

FIG. 18 shows sample measurement waveforms to illustrate an example ofweighing “on the fly” at a typical bar code sorter system transport beltspeed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to FIG. 1, a simplified electrical schematic diagram isshown illustrating one embodiment of a system for weighing articles onthe fly. In FIG. 1, a servo motor 110 is driven by a variable powersupply 120 which is coupled to a power source 122. In operation, currentflows through the motor to ground 124. A speed sensor (not shown) iscoupled to the motor 110 to provide a speed feedback signal 126. Varioussensors can be used such as shaft encoders, optical sensors, etc. toaccurately monitor speed or rotation of the motor 110. The speedfeedback signal is provided to an error amplifier 128, such as anop-amp, which compares the current speed to a predetermined input speedsetting 130. An error signal 132 related to the difference between thetwo inputs is input to the power supply 120 to control the motor currentthrough 110 so as to maintain the motor speed at the speed setting 130in the steady state. A change in the load on the motor, however, willresult in a transient in the motor torque indicative of that change inloading. That transient torque level may be captured as a proxyindicative of an impulse applied to the article.

Still referring to FIG. 1, the motor torque is monitored and a motortorque signal 140 related to the monitored torque level, for example adigital stream of samples, is input to a processor 142. This is notnecessarily a stand-alone processor, but it may be any programmabledigital processor, or a software component arranged to implement thedescribed functionality on a dedicated processor or as part of a largersystem. Article sensors 144, for example optical sensors (photodiodes,etc.), detect when each article of interest enters and leaves the weighstation, as further explained below with reference to other figures. Acalibration data store 148 stores calibration data, which can includesteady-state or “no load” measurements, taken when no article ispresent, as well as data taken from measurement of articles having knownmass. This data is used by the processor 142 to determine the articleweight, and the result is output, for example displayed, printed, orstored in digital file, as indicated at 150 in the drawing.

FIG. 2 is a mechanical drawing in top view of a belt-driven articletransport apparatus. In operation, articles move from right to left inthe drawing, from a first transport section, into a second transportsection (where a weigh station will be implemented as described below),and thence to a third or output transport section on the left. FIG. 3 isa mechanical drawing in top view showing greater detail of the secondtransport section of the apparatus of FIG. 2. Referring to FIG. 3,articles enter from the right through a variable pinch roller pair, pasta first photosensor, between a pair of fixed non-friction guides, andinto a first motor assembly. The first photo sensor, together withsecond and third photo sensors described below, generally correspond tothe article sensors 144 of FIG. 1. The first motor assembly comprises amotor driven hub, and an opposing spring-loaded pinch roller mounted ona pivot arm, controlled by a solenoid (not shown), for controllablymoving the opposing roller into contact or near contact with the saidhub so as to form a pinch roller pair for engaging the moving article.The first motor operates at the same speed as the belt-driven firsttransport section to normalize the speed of the article for articles ofdifferent lengths. Accordingly, each article enters the second transportsection at the same speed. The actual or absolute value of that speed isnot critical for present purposes. In contradistinction to prior art,the present system does not rely on speed measurements.

A second photo sensor detects movement of the article from the firstsection into the second section. The second section comprises a secondmotor assembly, similar to the first section. However, in accordancewith the present invention, the second section is modified by replacingthe common DC brush motor with a precision servo system furtherdescribed below. FIG. 4A comprises top view and cross-sectional views ofone example of an adjustable pinch roller assembly for use in thetransport apparatus of FIG. 2. FIG. 4B is a cross-sectional side view ofa pivot roller assembly of a type useful in the weigh station of FIG. 2.FIG. 4C is a side view of a pancake motor mounting in the articletransport apparatus of FIG. 2.

FIGS. 5-6 are mechanical drawings in top view illustrating a procedurefor replacing a pancake motor with a precision servo motor in theassembly of FIG. 2. The Teknic model M-2330 motor is just anillustrative example of such a servo motor. Other precision motors canbe used and should be considered equivalents. FIG. 7 is a side viewillustrating a precision servo motor installed below a transport deck ofa transport assembly with a sleeved hub installed for engaging anarticle moving through the transport assembly. Now we assume suchmodifications have been done, as described in the drawing, so that thesecond section motor assembly now employs a servo system in lieu of thepancake type motor used in the first and third transport sections. Athird photo sensor detects movement of the article from the secondsection into the third section. The third transport section (see FIG. 2)re-establishes the article speed to the system belt speed afterweighing.

Accordingly, in one embodiment, a transport mechanism (first section)projects an article at some initial velocity into the measuringapparatus. For example, in mail piece handling, a belt driven transportmechanism is commonplace. That velocity is known to the system itself(for such things as spacing the articles along their route), but itsvalue is not important and indeed is neither calculated nor used in theprocess of weighing the article. This ignorance by the weighingmechanism of the initial velocity of the article is material, since muchof the prior art measures mass by calculating the difference betweeninitial and final velocities of the article. Since the initial velocityis not provided to the weighing apparatus, such approach is precluded.

In one embodiment (see below for others) the article then enters ameasuring apparatus which pinches the article between two rollers. Inthe illustrative example in the drawings, the “measuring apparatus”generally corresponds to the second transport section, also referred toas a weigh station. The measuring apparatus has been commanded to outputthe article at a second velocity (which may be higher or lower than theinput velocity). This corresponds to the speed setting 130 of FIG. 1.The pinch rollers are driven by a servo mechanism (see FIG. 1) thatmeasures the angular velocity of a motor that drives one of the rollers,compares it to the desired angular velocity (at which the article wouldbe moving at the ordered output velocity), and supplies sufficienttorque to achieve the desired final angular velocity. The specificprofile of intermediate velocities ordered for or achieved by the systemare unimportant, though the proposed system includes devices thataccelerate and then decelerate the article (or the other way around) sothat its final velocity may be the same as its initial velocity. So, forexample, the weigh station may first accelerate, and then decelerate thearticle, arriving at the same velocity as the initial velocity, butgathering torque data in the meantime.

The solenoids that operate the pinch roller pivot arms are controlled sothat, while an article is in the second section (weigh station), asdetected by the photo sensors, the first and third transport sectionrollers are withdrawn from the motor hubs so that the weigh stationpinch roller assembly supports the article. In this way, accelerationand deceleration of the article are accurately reflected in the servoloop that drives the weigh station servo motor.

It is important to state that it does not matter what that final angularvelocity is. Unlike prior system, such as those disclosed on U.S. Pat.Nos. 7,096,152 or 3,648,839, the proposed system makes no absolutemeasurements at all. It works on calibration of torque, not absolutemeasurements of current or velocity.

The application of a precision instrument grade servo system to theproblem of weighing mail pieces or parcels while they are moving at ahigh speed enables multiple approaches to mass calculation. In apreferred embodiment, the servo mechanism is in continuous communicationand control of all of the moving roller system components prior tointroduction of the item to be weighed. In this way a state of nominalmotion or equilibrium can be established and related to the zero stateof the scale. (Recall zero state data can be stored in data store 148 ofFIG. 1.) Upon introduction of the subject article (which may be a mailpiece, a parcel, or other object), this equilibrium is disturbed.

The servo mechanism, by way of electronic and mechanical feedback loops,rapidly responds by injecting correcting signals to re-establish thenominal motion state. By measuring the error-correcting signalsgenerated by the servo system and scaling by a calibration factor, amass calculation can be made. Other methods of using servo data aredescribed later.

Since much of the prior art discusses calculating the weight (mass) ofthe articles, it bears mentioning here that the proposed system can workquite well with no actual calculation of article mass at all. All thatreally matters is the comparison of the mass-related property of thearticle to the mass-related properties of one or more calibrationarticles. Experimental data from a prototype is discussed later.

Other embodiments include but are not limited to the following:

-   -   Maintaining a state of angular momentum associated with the        nominal zero state and then measuring the incremental torque        required to re-establish the velocity of the nominal zero state        but now including an incremental mass (e.g. a mail piece).    -   Maintaining a nominal zero state of motion with an associated        constant torque and then measuring the difference in angular        displacement of the rotating components when an incremental mass        is introduced. The difference in angular displacement is        compared between the zero and the loaded state over equal and        fixed time intervals or over intervals whose ratio is known to        the system.    -   Maintaining a nominal zero state of motion with an associated        constant torque and then comparing the time differential        required to attain a fixed displacement.    -   Introducing an acceleration command and then measuring the        torque differential required to maintain that acceleration.

The normal friction forces on the motor and roller system will introducea negative acceleration on the system mass if a sustaining torque doesnot counter it. Since the friction force is constant, when anincremental mass is introduced, the system will have a differentacceleration in the absence of a sustaining torque. Since the frictionforce is constant, the differential acceleration would tend to besmaller for a larger mass. Therefore the torque required to maintain thevelocity of the now increased system mass would also be different. Wecan measure this incremental torque and compare with that of the zerostate of the system and also with a calibration factor to scale themeasurement.

Non-linear relationships between the mass-related property of thearticle and the measured property are also envisioned by the proposedsystem. In such a case sufficient calibration is required as toadequately define the relationships. It is not a requirement in everyembodiment that the article be propelled by a transport mechanism. Itcan for example, be self-propelled. In one embodiment, the object is atruck which moves at some measured velocity into the weighing apparatus.One possible system use is sorting the objects, such as mail pieces,into bins based on their determined weight (though this sortation is nota requirement of the proposed system). Another use may be to assesstaxes based on vehicle weight (for, say, a truck).

FIG. 9A is a top plan view of a transport assembly of a secondembodiment of an in-line weighing apparatus in a non-weighing state.This type of transport assembly may be integrated along a transporttrack of an automatic mail piece sorter machine, or the like, or may beimplemented in a stand-alone weighing machine. In general, a mail piece900 travels from left to right in the drawing. In FIG. 9A the mail piece900 is engaged between main transport belts 910 and 902 which movesynchronously at a predetermined system transport speed. This may be,for example, on the order of 150 inches per second. Belt 902 may bedriven and or guided by rollers 904, 906 etc. The left transport belt910 may be driven and or guided by rollers marked A, B and C forreference.

The left transport belt 910/902 conveys the mail piece 900 into aweighing station 950, further described below. After weighing, the mailpiece proceeds to exit the weighing station 950 by engagement in betweenright transport belt 918 and belt 902, again moving at the systemtransport speed. The right belt 918 is guided and or driven by rollersF, G and H as shown. These various belts are shown also in an explodedview in FIG. 10A. In the weighing station 950, the mail piece 900changes speed, perhaps more than once, but it does not stop. Thisexample has the advantage of maintaining a two-sided pinch to controlmail pieces as they travel through the system.

Turning now to the weighing station 950 in FIG. 9A, a front weigh belt960 is shown, driven by a motor 966 around a series of guide rollers L,M, N and O. The front weigh belt 960 is spaced apart from the mail piece900 in the non-weighing state shown in FIG. 9A. A rear weigh belt 940 isentrained on a series of guide rollers, generally as indicated, so thatbelt 940 also is spaced apart from the path of the mail piece 900 inthis non-weighing state. The weigh belts 940, 960 are spaced apart fromthe transport belts 902, 910, 914, 918 in the dimension into the page,so they do not conflict, as seen in the exploded view of FIG. 10A.(“Front” and “rear”are arbitrary labels in this description.)

FIG. 9B is a top plan view of the transport assembly of FIG. 9A in aweighing state. In this state, the mail piece 900 has entered the weighstation 950. The mail piece is disengaged from the transport belts asthe transport belts are repositioned into a weigh state spaced apartfrom the mail piece. To do so, guide rollers C,D,E and F are moved up asshown by the small arrows in FIG. 9B. Consequently, belts 910, 914 and918 do not contact the mail piece at this time. Rather, the mail pieceis now in contact with the rear weigh belt 940. In the lower portion ofthe drawing, the lower transport belt 902 is not affected. Rather, inthe weigh state, the front weigh belt 960 is repositioned to contact themail piece, so that the mail piece is gripped in between the front andrear weigh belts only. To reposition the front weigh belt guide rollersM and N are moved upward, as indicated by the small arrows in thedrawing. The belt 960 thus moves the mail piece temporarily off of thetransport belt 902 as further explained below.

The weigh belts are synchronized to the same speed, for example 250inches per second, which represents acceleration from the transport beltspeed (150 ips in the example). The weigh belts should be coupled to aprecision servo motor so that motion of the weighing belts translates toa corresponding rotation of the motor, and vice versa. In other words,there should be little or no slippage between the servo motor and theweighing belts. A separate motor may be coupled to each belt, as long asthe motors and respective belts are synchronized, or a single motor maybe used. Two motors are shown in the illustrated embodiment.

An example of a suitable servo motor is commercially available Teknicmodel M-2330. This is an instrument grade, brushless AC servo motor withintegrated encoder. Peak torque is on the order of 160 ounce-inches.Other precision motors can be used and should be considered equivalents.A high power density motor is preferred for building a weighing systeminto a confined space. The shaft encoder may provide, for example, onthe order of 4,000 to 8,000 counts per revolution.

As mentioned, FIG. 10A is an exploded view of the transport assembly ofFIG. 9A. In this view, a motor 946 drives the rear weigh belt 940. Asecond motor 966 drives the front weigh belt 960. A second (“lower”) setof front and rear weigh belts, 964 and 944, respectively, are shownbelow the transport belts 902 etc. These operate in the same manner asthe upper weigh belts 960, 940 as described. They should be synchronizedto the upper weigh belts, and may share common drive and controlelements. This may be termed an interleaved belt system, in that theweigh belts are above and below the transport belts.

FIG. 10B is an assembled, perspective view of the transport assembly ofFIG. 9A. Here is can be seen that the upper weigh belts (940,960) arelocated above the transport belts, and the lower weigh belts (arelocated below the transport belts. All three pairs of belts are sizedand spaced for engaging the mail piece 900—shown in dashed lines—at theappropriate times.

In operation of the assembly of FIGS. 9 and 10, a mail piece 900 isconveyed from left to right (FIG. 9A), initially by the transport belts.The intake transport belts are moving at a predetermined initialvelocity, for example the system transport speed in a sorter system, andthus the mail piece enters the weigh station at that initial velocity.Since the mail pieces may vary in length, for example from 5 inches to11.5 inches, short pieces would otherwise slow down before they hit themain rollers (weigh station) and produce a erroneous reading. To avoidthat result, the first pair of belts maintains the velocity of thesepieces, and then releases just as the piece reaches the main rollers.

Accordingly, when the mail piece arrives in the weigh station 950 (asdetected, for example, by photo sensors described later), the piece isreleased from the transport belts, and substantially immediately grippedin the upper and lower weigh belts (FIG. 9B), by the actions describedabove. This process may be enabled by a control system similar to theone described below.

In the weigh station, the piece may be accelerated and or decelerated bythe servo motor as discussed earlier to accomplish a weighing operation.The weigh belts thus change speed to make the measurement; the transportbelts preferably operate at constant speed. The piece then exits theweigh station, continuing to move from left to right in FIG. 9,essentially by reversing the above actions. That is, the assemblyswitches from the weigh state back to the non-weigh state. The weighbelts are disengaged from the mail piece, and substantially immediatelythe transport belts re-engage the mail piece. The mail piece may berestored to the initial velocity. In this way, a series of mail piecesmay move through the weighing station, and be weighed “in-line” withoutaffecting a larger system in which the weighing apparatus may beinstalled. Below we describe in more detail how the weight measurementsare electronically acquired.

FIG. 11A is a top plan view of a transport assembly of a thirdembodiment of an in-line weighing apparatus in a non-weighing state.Front and rear primary transport belts 1112 and 1102, respectively,convey a mail piece 1100 from left to right in the drawing. The mailpiece is gripped in between them, as shown, prior to weighing, and afterweighing. In this example, dimensions at 5-inch intervals are shown,based on an expected five-inch minimum mail piece length.

A second pair of transport belts 1122 front and 1120 rear, are arrangedto convey a mail piece, also at normal transport belt speed, when thesystem is not performing a weighing operation. The second transportbelts 1122, 1120 are spaced above the primary transport belts (as wellas the weigh belts), as best seen in the exploded perspective view ofFIG. 11C. The second transport belts “bridge the gap”in the non-weighingstate from the primary transport belts at the intake (left) side to thesame belts at the output (right) side as the primary transport belts arerouted around the weigh station. This embodiment ensures that even a5-inch envelope is pinched between two belts at all times.

A third pair of transport belts 1130, 1132 (FIG. 11C) are sized andarranged like the second pair, but are instead located below the primarytransport belts. In other words, these belts are interleaved, as bestseen in the exploded view of FIG. 11C. That is, the second pair oftransport belts 1120, 1122 are located above the primary transportbelts, while the third pair of belts 1130, 1132 are located below theprimary transport belts 1102, 1112. All three pairs of belts are sizedand spaced for engaging the mail piece 1100 at the appropriate times(and not during actual weighing of the mail piece). The total height ofthe three belts, plus spacing, would be similar to the minimum expectedheight of a mail piece, for example a 3-½ inch minimum for a standardletter. A pair of weighing belts 1114, 1116 are spaced apart from thetransport belts and do not contact the mail piece in this non-weighingstate (FIG. 11A).

FIG. 11B is a top plan view of the transport assembly of FIG. 11A in aweighing state. The mail piece 1100 has moved into the weighing station.The mail piece is released from the primary transport belts, and alsoreleased from the second and third pairs of transport belts. The mailpiece is now gripped between the weighing belts 1114, 1116 for weighing“on the fly” i.e., without stopping its travel. To do this, rollers Pand Q are repositioned to relocate the rear weigh belt 1114, asindicated by two small arrows, to bring the belt 1114 into contact withthe mail piece. This also brings the opposite face of the mail pieceinto contact with the stationary front weigh belt 1116. The mail pieceno longer contacts any of the transport belts. Weighing is conducted asthe mail piece moves along gripped in between the weigh belts. Asbefore, the weigh belts are coupled to a suitable, precision servomotor.

The piece then exits the weigh station, continuing to move from left toright in FIG. 11, essentially by reversing the above actions. That is,the assembly switches from the weigh state back to the non-weigh state.The weigh belt 1114 is disengaged from the mail piece, and consequentlythe transport belts re-engage the mail piece. In particular, dependingon the size of the mail piece, the second and third transport beltsensure that the piece moves along into re-engagement with the primarytransport belts 1102, 1112 on the exit (right) side of the assembly. Themail piece may be restored to its initial velocity. FIG. 11D shows thetransport assembly in an assembled, perspective view, without a mailpiece.

FIG. 12 is a simplified system diagram of a dual-servo controlled,in-line weighing apparatus in a postal sorting system. This is called“dual-servo” as a first servo loop controls a first servo motor for aweighing operation, and a second servo loop controls a second servomotor for gripping tension control during the same weighing operation.In the illustrated embodiment, a transport 1200, typically comprisingmoving belts, moves a stream of mail pieces from right to left in thedrawing. Such transports may move the mail at speeds on the order of 10ft./sec although the particular speed is not critical to thisdisclosure. We refer to this quantity as the “system speed” or“transport speed.”

At the right or intake side of the drawing, a “PHOTO EYE #0” comprises alight source and a corresponding photo detector 1202, arranged to detectthe arrival of an incoming mail piece (not shown) as the leading orfront edge of the mail piece traverses the light beam. The resultingelectrical signal can be used to trigger a camera 1204 to start a newimage capture. The camera then uploads image data to an image captureand processing component 1214. This process preferably is implemented insoftware, and may be implemented in the ILS Processor 1212 in someembodiments. The image capture process 1214 stores the mail piece imagedata in a datastore 1218. In some embodiments, the system may be coupledto another database, e.g. an postal service ICS database, in which casethe image data may be stored there. After weighing, the ILS Processorstores the determined weight of a piece in the database 1218 inassociation with the corresponding image data.

The image capture process 1214 may utilize an OCR engine (software) 1216to extract or “read” a destination address, or at least ZIP code, fromcaptured mail piece image. These components may communicate over a localnetwork 1240, for example an Ethernet network. Destination address dataalso may be stored in 1218 in association with the item image or otheridentifying data. In an embodiment, ID Tag data from an ICS may be usedas an identifier.

Another database 1280 stores data for a batch of mail to be weighed inthe ILS. The database 1280 may include information about the mail piecesin the batch and the postage paid for mailing the pieces. The database1280 may include data or a machine-readable “manifest” provided by asender or pre-sort house. For example, it may have a list of the mailpieces in the batch. They may be listed individually, by destinationaddress, destination postal code, or using an internal ID number. Or,there may simply be a listing of the numbers of items, in total, or perzip code range, or per individual zip code. Other variations may beprovided by a mailer for its own internal purposes.

The database 1280 preferably includes postage information as well. Thismay be the actual amount of postage paid for each individual item, whereindividual items are listed. Alternatively, summary data may be usedwhere mail pieces are grouped or aggregated such that a bunch of itemshave the same postage paid. The database 1280 may include mailer permitinformation, postage rates, discounts, etc. Using this information, theILS Processor 1212 or another process can correlate the mail piecesreflected in the manifest in database 1280, with the weights of thecorresponding pieces, stored at 1218. It can determine the appropriatepostage for each piece, and compare the actual postage paid for thepiece. The difference, if any, is owed to the postal service (assumingthe subject mail piece is processed by the postal service). In someapplications, this system may be used to correct the postage for a batch(or individual items) before submission to the postal service.

Next we proceed to the weighing operations. After the envelope passes bythe camera 1204 (again, moving right to left in the drawing), a secondphoto detector pair (“PHOTO EYE #1) 1220 detects the leading edgeentering the in-line scale or weighing region. The photo detector 1220is coupled to a scale system controller 1230. A third photo detectorpair 1232, and a fourth photo detector pair 1234 also are coupled to thescale system controller 1230. Operation of these devices is describedbelow. The scale system controller 1230 may be connected by any suitabledata network arrangement, such as an Ethernet network 1240, forcommunication and data transfers with other components as indicated inthe drawing, and with the sorter system controller (not shown).

Referring again to FIG. 12, a first servo control system is driven bythe measurement servo controller 1250. The photo detector 1232 iscoupled to the measurement servo controller, as shown, to detect a mailpiece entering the weigh station. In addition, the photo eye detects thetrailing edge of the mail piece, which indicates that the piece hascleared the pinch roller #1 and therefore is ready for weighing. Themeasurement servo controller is coupled to a capstan motor 1252 forweighing operations. During a weighing operation, the mail piece isgripped between a capstan roller coupled to the capstan motor 1252, andan opposing pinch roller 1254. The pinch roller, in a preferredembodiment, is linked to the capstan roller to keep them synchronized.For example, in an embodiment, rather than a freewheeling pinch roller,the pinch roller 1254 opposing the capstan roller also is powered by thecapstan servo motor 1252. FIG. 13 illustrates such an embodiment,further described below. This arrangement increases the availablefriction surface area and reduces roller slippage to improve weighingaccuracy.

In addition, the weigh station pinch roller 1254 may be mounted on anactive swing arm assembly, as distinguished from a traditionalspring-loaded swing arm. Here, the swing arm is coupled to a tension armservo controller 1260 which is arranged to present a constant force oneach mail piece during weighing regardless of thickness. A passivespring system, by contrast, presents increased force (due to increasedspring compression) on thicker mail pieces. One example of an activeswing arm assembly is described below with regard to FIG. 13.

Two additional capstan and pinch roller assemblies provide speednormalization for mail pieces of varying length. A capstan 1266 andopposing pinch roller 1268 ensures that all mail pieces are presented tothe measurement rollers in the weigh station at uniform velocity.Another capstan 1270 and opposing pinch roller 1272 restores each mailpiece to the original transport speed. These capstans may be controlledby a speed controller 1274. These outboard pinch rollers may becontrolled (opened and closed) by the scale system controller 1230.

The controller coordinates their actions, based on input from the photodetectors, to grip a mail piece in the weigh station assembly (1252,1254), immediately after releasing it from the input side pinch rollerassembly (1266, 1268) or at substantially the same time as the piece isreleased, so as to minimize slowdown. Preferably, the grip in the weighstation is fast and firm, so as to minimize slippage in the rollers. Forexample, the force applied may be on the order of two pounds force. Inan embodiment, this gripping force is applied by the tension arm motor,under a precise servo control, and further described below. Slippage isalso minimized by synchronized, active drive of the capstan roller andthe pinch roller, rather than using a passive pinch roller. In anotherembodiment, a lesser gripping force may be applied. A system may beprogrammed to wait, for example on the order of 10 msec, to ensure thatthe piece has stopped slipping.

In one embodiment, the servo controller 1250 receives speed feedbackfrom the capstan motor 1252, and drives the motor as programmed. Forexample, it may be arranged to accelerate or decelerate the mail pieceby a predetermined amount. The servo loop must be fast and accurateenough to accelerate (and/or decelerate) a mail piece as commandedwithin a time frame that is practical for in-line applications. Suitableservo motors and amplifiers are described above. Preferably, weighing ofone piece is done within approximately 40 msec. The motor torque profileacquired during that acceleration can be analyzed to determine weight ofthe mail piece. The acceleration produces a spike or impulse in motortorque that may be captured and analyzed to determine weight. Bycontrast, a constant velocity in this scale would not work.

In other embodiments, mentioned above, the servo system may not seek toaccelerate or decelerate the piece to a new velocity. Rather, it mayinject an impulse to maintain a zero weight state.

FIG. 13 is a side view of an embodiment of an in-line weighingapparatus, installed on a platform or deck 1300 made of a sturdy, rigidmaterial such as steel. The deck may be, for example, on the order of1.0 cm thick, but this dimension is not critical. The deck surface mustbe substantially flat and smooth so as to provide a surface for mailpieces to glide over it without significant friction. A first roller(intake roller) 1302 is part of a capstan (1402) and opposing pinchroller pair, better seen in FIG. 14 top view. This is an intake rolleras a mail piece travels from left to right in the drawing, as indicatedby the arrow 1400 in FIG. 14. A similar output roller 1304 is again partof a capstan (1404) and pinch roller pair as shown in FIG. 14 in topview.

In operation, the intake capstan 1402 operates (CCW) at the same speedas a belt-driven transport section, if the weighing apparatus isinstalled in a larger machine such as a sorter, to normalize the speedof a mail piece for pieces of different lengths. This enables allincoming pieces to enter the weighing assembly at the same speed. Theactual or absolute value of that speed is not critical for presentpurposes. In contradistinction to prior art, this system does not relyon speed measurements.

Referring again to FIG. 13, a weighing assembly 1310 includes a CapstanRoller, driven by a Capstan Motor 1312, via a shaft 1318 (see FIG. 16)which passes through the deck 1300. All the rollers (1302, 1402, CapstanRoller, Pinch Roller 1316, 1304, and 1404 are located above the deck1300 for conveying mail pieces (left to right) over the surface of thedeck. The various motors, gears and belts, described below, preferablyare located below the deck, leaving a clear path for the moving mailpieces. In another embodiment, the drive mechanics may be located abovethe deck.

Capstan Motor 1312 also indirectly drives an opposing Pinch Roller 1316(see FIG. 14), so that the Capstan Roller and Pinch Roller are preciselysynchronized. This minimizes roller slippage to improve weighingaccuracy. Referring now to FIG. 15, the Capstan Motor 1312, shaft 1318,drives Belt1, which in turn is linked to the opposing Pinch Roller 1316as follows. The Capstan Motor shaft 1318 (CCW) drives Belt1, which inturn drives an Gear1. Gear1 is mounted co-axially on a bearing on shaft1332 of the tension arm motor 1330, so that Gear1 is free to rotateindependently of the shaft 1332. An idler Gear2 is engaged with Gear1,so that rotation of Gear1 drives Gear2 clockwise, as indicated by arrowsin the drawing. Force applied by the tension arm motor 1330 does notaffect the operation of Gear1 or Gear 2. (The role of the tension armmotor is described below.) See also the perspective view in FIG. 16.Gear2, driven by Gear1 as noted, in turn is arranged to drive a Belt2 inCW rotation as shown in FIG. 15. Belt2 in turn is arranged to rotate apulley 1340, which is mounted to a shaft 1314 to drive the Pinch Roller1316.

Note the presence of a rigid tension arm 1320. The tension arm ismounted at one end on shaft 1332 of the tension arm motor 1330. Thetension arm 1320 supports the idler Gear2 which is mounted on a bearingfor free rotation. The other end of the tension arm, opposite thetension arm motor, comprises a generally cylindrical housing 1320(a),although the exact shape is not critical. Housing 1320(a) has a shaft1314 rotatably mounted therein, for example in a bearing assembly (notshown). The shaft 1314 extends upward through the deck 1300 to drive thePinch Roller. The shaft is driven by Belt2 by means of a pulley 1340mounted on the shaft 1314. FIG. 16 is a perspective view of theweighting assembly 1310, showing the deck in phantom for clarity. FIG.17 is a perspective view of the tension arm 1320 standing alone. Thisdesign is merely an example and not intended to be limiting.

In operation, the tension arm motor 1330 rotates the tension arm througha limited range on the order of approximately +/− 10 degrees from aneutral or center setting. The exact range of motion is not critical.This rotation serves to adjust the position of the pinch roller 1316, asit is mounted to the tension arm as mentioned. An oblong slot 1315 inthe deck accommodates this motion (see FIG. 16). Because the CapstanRoller is fixed in position relative to the deck, repositioning thePinch Roller has the effect of adjusting the pinching force between theCapstan Roller and the opposing Pinch Roller, to keep it constant.

The tension arm motor 1330 preferably is driven by a precision servocontrol system, so that it provides a selected constant force on thePinch Roller. This feature is distinguished from other systems in whichpinch rollers generally are urged against the capstan roller by aspring. Springs provide a tension or force that varies with distance(compression of the spring). A spring therefore would cause the tensionin a mail system to vary with the thickness of each mailpiece,interfering with weighing operations as described herein. The systemdescribed above provides a constant force for gripping a mail piece inthe weighing apparatus independent of the thickness of the mail piece(within reasonable bounds). Note that tension arm servo controller datacan be used to record mail piece thickness if desired.

In a preferred embodiment, a motion damper 1390 is fixed to the deck andarranged to apply a damping force to the tension arm to suppressvibration of the tension arm when it closes on a mail piece at highspeed. The damper shaft and piston are connected to the tension arm. Atension arm motion damper may be commercially available Ace Controls,model MA 225 or similar.

In a preferred embodiment, a capstan motor may be a commerciallyavailable servo motor such as Teknic model M-2311P or similar. Thecapstan motor may be controlled using, for example, a servo amplifiersuch as Teknic model SST-E545-RCX-4-1-3 or similar. In these amplifiers,also called servo drives, a high-speed DSP control processor controlsall of the feedback loops: position, velocity and actual torque. Torqueis actively measured and controlled, with losses in the motoreffectively minimized. The operation is substantially all-digital: themotor measurements are converted directly into digital format for theDSP and the outputs to the motor are digital PWM pulse streams. Inalternative solutions, analog processing may be used, as long as theperformance characteristics described herein are met.

The tension arm motor may be a commercially available servo motor suchas Glentek model GMBM-40100-13-0000000 or similar (Glentek, El Segundo,Calif.). This too is a brushless AC servo motor. It provides a 100 Wpower rating, 3000 rpm rated speed, and has a peak stall torque of aboutnine lb-inches. It may be controlled with a servo amplifier such asGlentek—SMA9807-003-001-1A-1 or similar. In operation, the servoamplifier can provide output data, in analog or digital form, thatindicates torque applied to the motor as a function of time.

In an embodiment, mail pieces travel into and leave the scale at a speedon the order of 13 feet/second (156 inches per second). As noted, theexact transport speed is not critical. In a preferred embodiment, thesystem can calculate weight of each piece in real time. That leavesabout 70 msec available for each measurement. Within that time, a systemmay capture, for example, 128 sample measurements from the capstan servomotor amplifier. Weighing accuracy should be within a range ofapproximately +/− 7 grams (0.25 ounce). Prototypes have demonstratedaccuracy on the order of +/− 4 grams (0.14 ounce).

FIGS. 8A and 8B are oscilloscope traces of capstan servo motor torquemeasurements taken in a development prototype weighing system thatimplements aspects of the present invention. This data may be analyzedin various ways, for example using one or more suitably programmeddigital processors. Preferably, a real-time system determines a weightof a mail piece from the corresponding servo amplifier data quicklyenough that pieces can continue to move through the in-line scale atnormal sorting system speeds. For example, 128 servo samples over 30msec would require a data rate of around 4 k samples/sec.

FIG. 8A depicts a 5 gram differential torque measurement from a weigh onthe fly prototype. Trace “C” is 12 grams, “B” is 17 g and “A” is 22 g.Vertical scale is ounce-inches of servo motor torque and horizontal istime (on the order of 10 msec per division). The first vertical cursoron the left is the point at which the mail piece trips the photo eye forthe center roller (weighing) system. The other cursors are not relevant.It is straightforward to calibrate the system by weighing mail pieces ofknown weights.

FIG. 8B shows traces of 2.5 gram differential. The “E” line is 14.5 gand trace “D” is 17 g. These waveforms are of slightly different shapefrom the previous image due to increased oscilloscope gain and differentmechanical settings on the test bed transport. These traces show clearresolution even down to 2.5 grams. We believe this can be extended toconsiderably finer resolution while continuing to process at full speed(e.g. 40,000 pieces per hour).

In an embodiment, it is helpful to conduct a Fourier analysis on thetorque waveform sample data. The discrete Fourier transform (DFT) may beused to reduce the data to a small number of values or coefficients. TheDFT can be computed efficiently in practice using a fast Fouriertransform (FFT) algorithm. By pre-computing the same analysis on knowncalibration pieces, the Fourier coefficients of interest may be stored,for example in a lookup table, to determine weights later duringoperation by comparison to the values in the table. This approachprovides an effective way to compare the torque waveforms to provideaccurate measurements. It also helps to filter out vibration and othersystem noise from the measurement data.

In one embodiment, an in-line scale system of the type described abovemay be deployed within or in tandem with automated mail handlingequipment such as a destination bar code sorter machine (DBCS). On thebar code sorter system in this example, the transport belt speed is 153ips. The capstan servo on the ILS runs at 250 ips tangential velocity.The shortest mail piece is 5 inches long, plus a 3.5 inch minimum gapbetween pieces. So at an incident speed of 153 ips, we have ameasurement interval of approx 56 ms between pieces. This timing isillustrated in the upper trace of FIG. 18. The system therefore needs tocomplete all sampling and processing in this interval to operate in“real time”.

In a preferred embodiment, the system acquires 128 samples to the FFT,and the servo system described above samples at 1750 samples per second.This means that the sampling interval per piece is approx 73 ms.However, as noted, in the present example, only about 56 msec isavailable between pieces. One solution to this apparent dilemma is tosimultaneously sample into 2 separate measurements that are offset intime. The system thus is multi-threaded. We center the torque impulsedata for each piece in the 73 ms window so any data that appears insequential measurements is where the servo is quiescent or betweenpieces. This is essentially the zero area. This overlap technique isillustrated in FIG. 18. In the top figure, the time between the leadingedge of the impulses is 56 ms because the pieces are 5 inches longseparated by 3.5 inches. In the bottom figure, the pieces are 8 incheslong so the sampling overlap is smaller. The gaps is constant at 3.5inches.

Other Embodiments and Variations

An alternative embodiment to the pinch roller system discussed above isabove is to use a forced air column opposite the servo roller in placeof the pinch roller. This approach has several potential advantages: Theentry impulse will not be effected by thickness since there will be nopinch roller and swing arm to displace. Moreover, the force imposed bythe air column will be constant and not variable with thickness.

The air column can be switched rapidly thereby allowing the torquemeasurement to be taken after the leading edge of the piece has passed.The air column could actually keep the servo roller clean. Yet anotherembodiment uses gravity to hold the article against theimpulse-providing mechanism. It is preferred, however, to apply positivecontrol of the article as explained above.

It is not necessary for the proposed invention that theimpulse-providing device rotate. All that is necessary is that itprovide an impulse to achieve an ordered final state of motion of thearticle, that the power (electrical or other) that provides the impulsebe measured, and that the results be compared with the results ofproviding impulse to objects of known properties passing through thesystem.

It is not necessary for the proposed system that the impulse provided tothe article be tangential to the article. It can, for example, betransverse. What matters is that the system has an initial state, afinal state, and a method for measuring some stand-in indicative of theimpulse that moves the object from its initial to its final state. Itthen must compare that measurement with the measurement of the stand-inrequired to change the state of one or more articles of knownmass-related properties.

In one embodiment the mass-related property of the article is deduced byinterpolating between the mass-related properties of calibrationarticles. This interpolation may be linear, polynomial, or any othermethod.

In another embodiment the article's mass-related property may bedetermined to be larger than or smaller than some threshold withoutdetermining either the article or the calibration object's actualmass-related property. Thus if an object of maximum mass were used forcalibration, and if objects of mass greater than this maximum are to berouted from the system, it is sufficient to know whether or not thearticle to be measured is more massive than the calibration mass.

Postage Checking and Franking

Referring once again to the control system of FIG. 12, a mail processingsystem may include an in-line weighing apparatus, discussed above, and adatastore 1280 for storing postage information. Postage information mayinclude postage rates, for pieces of various sizes, classes and weights.In an embodiment, a scale system may be configured to process aparticular run or batch of mail, for example a batch of standard sizeletters. Discounts may be applicable for batches that meet certainvolume and other requirements (e.g. presorting). This configuration datamay be stored at a configuration and logging datastore 1282 in thesystem of FIG. 12. The system can access appropriate postage rates fromthe datastore 1280, which may be coupled to a system network, e.g.Ethernet 1240.

In operation, a system of the type illustrated by FIG. 12 may weigh amail piece, log the weight (1282), and check whether or not the correctpostage has been paid for that piece. This may be done, for example, bythe in-line scale processor 1212 consulting the postage data inrepository 1280. The repository data may include various types ofpostage data. For example, it may store the postage per piece that waspaid for a specific pre-sort batch of mail. The batch may be identifiedby any suitable means, for example, mailer ID, batch ID, date/timestamps, etc. For a pre-sort batch, a single postage amount may be paidper piece. The present system can check whether in fact each weighedpiece has a weight within the limit for the amount paid per piece.Overweight (or “postage due”) pieces may be logged and counted in orderfor the USPS to collect the shortfall from the mailer. Specificmailpieces may be identified for example using ID Tag numbers. Or justthe number of postage due pieces may be tallied.

In another scenario, the postage paid for each specific mailpiece may bestored at 1280, and the system can verify whether or not the correctpostage was paid for that piece. That test may involve weight, size, andother characteristics listed below. For example, the mail piecedimensions may be determined from the image capture and analysiscomponents, or using photocells. Again, data may be logged, andpostage-due pieces can be flagged in a database and or marked on themail piece itself. Marking may be done by printing, spraying, etc. usingknown techniques. The postage-due marking may comprise amachine-readable indication for special handling. Or the pieces may notbe specially marked, but a report and invoice automatically generated tocharge the mailer for the postage due. Or, the postal service can simplydebit the mailer by credit card, ACH account, etc. Using aspects of thepresent invention, the USPS can collect revenues, otherwise lost, with aminimum of extra effort. Indeed, the collection process just describedmay be fully automated, with resulting increased revenues to the USPSestimated to be worth tens or even hundreds of millions of dollars.

The actual postage paid for mail pieces that are not in a pre-sort batch(called letterbox pieces) may be determined outside the systemillustrated, for example by human visual inspection, and stored indatastore 1280 for checking. Or, the postage may be determined in asorter or other automated handling system using an image capture systemthat captures and processes an image of the mail piece front side. Thismay be the same imaging system as that used for address recognition, oranother one. In FIG. 12, a camera 1204 (bar code reader) is coupled via1210 to an image capture system 1214. For example, datastore 1218 maystore image data related to postage stamps or postage meter markings.The system may compare captured image data from the mail piece to thestored postage image data (indicia) to recognize the postage paid forthe mail piece.

Methods for postage recognition include the following:

-   -   Postal stamp recognition by optical imaging and software        recognition    -   Postal permit recognition by optical imaging and software        recognition    -   Indicia recognition by hardware or software system e.g. 2-D        barcode (IBI)    -   Barcode recognition with embedded weight specification and        originator identification    -   Keyline recognition with embedded weight specification    -   The lookup and reference of a postal permit database with        associated payment information

One type of machine-readable imprint, approved by the USPS, is calledIBI or Information-Based Indicia. IBI in one embodiment comprises atwo-dimensional bar code printed with an embedded digital signature. TheIBI imprint contains identifying information identifying the postagemeter that made the imprint, and the postage paid. IBI is thecombination of a machine-readable barcode and human readableinformation. The digital signature serves to authenticate that theinformation is not tampered with in any way.

To summarize, one aspect of the present invention comprises a system formeasuring the weight of each mail piece in a stream of mail pieces,determining the proper postage for that mail piece, determining theamount of postage paid by the mailer, and segregating out mail pieceswith improper postage. The proper amount of postage may be based on themail piece's weight, size, thickness, mailing point, delivery point, orother property, alone or in combination. Another aspect of the inventioncomprises a method for ensuring that proper postage has been paid foreach mail piece.

While the disclosed system is primarily aimed at determining which mailpieces have too little postage for their weight and othercharacteristics, it is within the purview of this disclosure to be ableto audit and/or sort individual and sets of mail pieces based on anycombination of the above attributes or others. For example, while postalauthorities generally quantize their charges (for example charge X forletters up to 1 ounce, Y for letters weighing greater than one ounce andup to two ounces, etc.), it is within the purview of this invention tobe able to audit and/or sort mail pieces by levels of attributes thanmay be more (or less) finely distinguished than the official categories.

The measured attribute(s) of the mail piece may include its weight(using a scale such as the in-line scale); its size or dimensions(measurable, for example, by a set of lights and photocells, the pathsbetween some of which are interrupted for a period of time by the mailpiece); its thickness (measurable, for example, by an offsetting pinchroller or laser thickness detector); its point of origination(determinable by the location of the initially-scanning mail sortationsystem or its return address; its intended destination (determinablefrom the delivery address on the mail piece); and others, either aloneor in combination.

In one embodiment, the result of the process described above may includeflagging out of compliance mail pieces for real time sortation to rejector overweight bin for return to sender or postage pending hold process.In another embodiment, as noted above, the mail piece may not bespecially handled at all, but the postage due automatically charged tothe sender. Audits of a mail stream may be produced and of individualmailers to determine the distribution of their mailing as to weight andas to whether they are overweight for the applied postage.

A high-speed franking machine may be used in combination with an in-linescale of the type disclosed above. By “high-speed” we mean a contrivancethat can process mail pieces at normal transport speeds, for example onthe order of 150 inches per second, or 40-60 thousand pieces per hour.This may be combined with the in-line scale to apply the correct postageto each piece, based on its weight, as the pieces move through automatedhandling in real-time. In this application, there is no need to check orverify postage, since the known correct postage is applied to each pieceafter weighing. Such a method and system may be used by senders(businesses or pre-sort houses) to ensure that correct postage isapplied, and it can be done in combination with the a sorting process,by modification of a sorting machine. Just as an in-line scale can bedeployed into a sorter, taking for example about 24 inches of lineartransport space in typical application, so too the franking machine maybe inserted following the scale on a single system. In otherembodiments, a “scale plus franking machine” may be used separately toapply postage before sending a batch of mail to pre-sort.

Hardware and Software

Several examples have been described above with reference to theaccompanying drawings. Various other examples of the invention are alsopossible and practical. The system may be exemplified in many differentforms and should not be construed as being limited to the examples setforth above. The system described above can use dedicated processorsystems, micro controllers, programmable logic devices, ormicroprocessors that perform some or all of the operations. Some of theoperations described above may be implemented in software or firmwareand other operations may be implemented in hardware.

For the sake of convenience, the operations are described as variousinterconnected functional blocks or distinct software modules. This isnot necessary, however, and there may be cases where these functionalblocks or modules are equivalently aggregated into a single logicdevice, program or operation with unclear boundaries. In any event, thefunctional blocks and software modules or features of the flexibleinterface can be implemented by themselves, or in combination with otheroperations in either hardware or software.

Digital Processors, Software and Memory Nomenclature

As explained above, aspects of the invention may be implemented in adigital computing system, for example a CPU or similar processor in asorter system, in-line scale (standalone), or other embodiments. Morespecifically, by the term “digital computing system,” we mean any systemthat includes at least one digital processor and associated memory,wherein the digital processor can execute instructions or “code” storedin that memory. (The memory may store data as well.)

A digital processor includes but is not limited to a microprocessor,multi-core processor, DSP (digital signal processor), GPU, processorarray, network processor, etc. A digital processor (or many of them) maybe embedded into an integrated circuit. In other arrangements, one ormore processors may be deployed on a circuit board (motherboard,daughter board, rack blade, etc.). Aspects of the present invention maybe variously implemented in a variety of systems such as those justmentioned and others that may be developed in the future. In a presentlypreferred embodiment, the disclosed methods may be implemented insoftware stored in memory, further defined below.

Digital memory, further explained below, may be integrated together witha processor, for example RAM or FLASH memory embedded in an integratedcircuit CPU, network processor or the like. In other examples, thememory comprises a physically separate device, such as an external diskdrive, storage array, or portable FLASH device. In such cases, thememory becomes “associated”with the digital processor when the two areoperatively coupled together, or in communication with each other, forexample by an I/O port, network connection, etc. such that the processorcan read a file stored on the memory. Associated memory may be “readonly” by design (ROM) or by virtue of permission settings, or not. Otherexamples include but are not limited to WORM, EPROM, EEPROM, FLASH, etc.Those technologies often are implemented in solid state semiconductordevices. Other memories may comprise moving parts, such a conventionalrotating disk drive. All such memories are “machine readable” in thatthey are readable by a compatible digital processor. Many interfaces andprotocols for data transfers (data here includes software) betweenprocessors and memory are well known, standardized and documentedelsewhere, so they are not enumerated here.

Storage of Computer Programs

As noted, aspects of the present invention may be implemented orembodied in computer software (also known as a “computer program” or“code”; we use these terms interchangeably). Programs, or code, are mostuseful when stored in a digital memory that can be read by one or moredigital processors. We use the term “computer-readable storage medium”(or alternatively, “machine-readable storage medium”) to include all ofthe foregoing types of memory, as well as new technologies that mayarise in the future, as long as they are capable of storing digitalinformation in the nature of a computer program or other data, at leasttemporarily, in such a manner that the stored information can be “read”by an appropriate digital processor. By the term “computer-readable” wedo not intend to limit the phrase to the historical usage of “computer”to imply a complete mainframe, mini-computer, desktop or even laptopcomputer. Rather, we use the term to mean that the storage medium isreadable by a digital processor or any digital computing system asbroadly defined above. Such media may be any available media that islocally and/or remotely accessible by a computer or processor, and itincludes both volatile and non-volatile media, removable andnon-removable media, embedded or discrete.

It will be obvious to those having skill in the art that many changesmay be made to the details of the above-described embodiments withoutdeparting from the underlying principles of the invention. The scope ofthe present invention should, therefore, be determined only by thefollowing claims.

The invention claimed is:
 1. A method for weighing a moving article, comprising: receiving an incoming article having a first velocity; gripping the incoming article between a pinch roller and a capstan roller; synchronizing rotation of the pinch roller and the capstan roller to each other to avoid slippage of the article gripped between them; providing a capstan servo motor having a shaft operatively coupled to the capstan roller so that the motor shaft and the capstan roller rotate in unison; providing a servo amplifier coupled to the capstan servo motor so as to form a closed-loop servo system for driving the motor and for monitoring actual torque applied by the motor; in the servo amplifier, prior to said gripping the article, commanding the servo motor to a predetermined, constant command speed that is different from the first velocity of the incoming article; beginning after the article is gripped between the pinch roller and the capstan roller, acquiring a series of capstan servo motor torque sample data as the mail piece moves through pinch roller and capstan roller, so that the captured torque data reflects the torque applied by the capstan servo motor to change the article speed from the first velocity to the command speed; and processing the acquired torque data to determine a weight of the article without regard to actual speed of the article.
 2. A method according to claim 1 wherein said processing the acquired torque data includes: forming an acquired torque data waveform responsive to the acquired servo motor torque sample data; and comparing the acquired torque data waveform to a stored calibration torque data waveform.
 3. A method according to claim 2 wherein said comparing step includes: applying a Fourier transform to the acquired torque data waveform to determine acquired torque data waveform coefficients; applying a Fourier transform to the stored calibration torque data waveform to determine calibration coefficients; and comparing the acquired torque data waveform coefficients to the calibration coefficients to determine the weight of the article.
 4. A method according to claim 2 wherein applying a Fourier transform to the stored calibration torque data waveform to determine calibration coefficients is computed in advance, and the calibration coefficients stored in memory.
 5. An in-line weighing apparatus comprising: an intake transport belt assembly arranged for moving a mail piece along a predetermined transport path at a predetermined intake transport speed; a weighing station positioned along the transport path to receive a mail piece from the intake transport assembly while the mail piece is moving at substantially the transport speed; the weighing station arranged for gripping a mail piece after the mail piece is released from the transport belt assembly; the weighing station including a capstan servo motor arranged to rotate in synchrony with the moving mail piece; a capstan servo controller coupled to the capstan servo motor to drive the capstan servo motor to a predetermined, constant command speed that is different from the transport speed; the capstan servo controller also arranged to acquire motor torque data from the capstan servo motor as the mail piece moves through the weighing station, so that the captured torque data reflects the torque applied by the servo motor to change the mail piece speed from the intake transport speed to the command speed; and a processor arranged to determine a weight of a mail piece from the captured torque data.
 6. The in-line weighing apparatus according to claim 5 including: a pair of weigh belts in the weigh station, arranged for gripping a mail piece between them after the mail piece is released from the transport belt assembly; the capstan servo motor arranged to synchronously drive the pair of weigh belts; and the servo controller arranged to acquire motor torque data from the capstan servo motor as the mail piece moves through the weighing station gripped between the pair of weigh belts, so that the captured torque data reflects the torque applied by the capstan servo motor to change the mail piece speed from the intake transport speed to the command speed.
 7. The in-line weighing apparatus according to claim 6 and including: a first photocell positioned along the transport path for detecting when a mail piece enters the weighing station; a first set of repositionable guide rollers arranged for moving the weigh belts into proximity with one another for gripping the mail piece in between them; a second set of repositionable guide rollers arranged for moving the intake transport belts away from the mail piece so as to release it; and a scale system controller coupled to the first photocell for detecting when a mail piece enters the weighing station, and coupled to the first repositionable guide rollers for repositioning the guide rollers so as to move the weigh belts into proximity with one another for gripping the mail piece in between them responsive to a mail piece entering the weighing station, and the scale system controller further coupled to the second repositionable guide rollers for repositioning the guide rollers so as to move the intake transport belts to release the mail piece responsive to the mail piece entering the weighing station, whereby the mail piece is gripped solely by the weigh belts during a weighing operation.
 8. The in-line weighing apparatus according to claim 7 and including: a first memory for storing servo motor torque data acquired from the servo controller during a weighing operation; a second memory storing calibration data; and wherein the processor is coupled to the first and second memories for determining a weight of a mail piece by comparing the acquired motor torque data to the stored calibration data.
 9. The in-line weighing apparatus according to claim 8 and wherein: the processor is arranged to calculate a Fourier transform of the acquired motor torque data; the stored calibration data comprises Fourier transform coefficients; and the processor determines the weight by comparing the calculated Fourier transform of the acquired motor torque data to the stored calibration Fourier transform coefficients.
 10. The in-line weighing apparatus according to claim 8 and wherein the torque data is acquired over a measurement period of less than approximately 70 msec in order to weigh a mail piece in real time at a typical transport speed.
 11. The in-line weighing apparatus according to claim 10 and wherein the torque data acquired over a measurement period comprises a number of digital samples equal to an integral power of two samples.
 12. The in-line weighing apparatus according to claim 8 and wherein the exit transport speed is equal to the intake transport speed.
 13. The in-line weighing apparatus according to claim 8 and wherein the command speed is greater than the intake speed, so the mail piece is accelerated in the weighing station by the capstan servo motor, giving rise to a motor torque impulse.
 14. The in-line weighing apparatus according to claim 8 and wherein the servo motor comprises an instrument grade, brushless AC servo motor with integrated encoder.
 15. The in-line weighing apparatus according to claim 8 and wherein the weigh belts comprise an upper pair of weigh belts disposed above the transport belts, and a lower pair of weigh belts disposed below the transport belts.
 16. An in-line weighing apparatus comprising: a primary transport belt assembly arranged for moving a mail piece along a predetermined transport path at a predetermined transport speed; the primary transport belt assembly including a pair of transport belts for gripping a mail piece between them, the pair of transport belts arranged to insert the mail piece into a weighing station and also routed around the weighing station and arranged to receive a mail piece when it exits the weighing station; a weighing station positioned along the transport path and located to receive a mail piece from the primary transport belt assembly for weighing the mail piece while the mail piece is moving along the transport path, by changing the speed of the mail piece; the weighing station including a pair of weigh belts arranged for gripping a mail piece between them for weighing; and the weighing station including means for capturing data that describes an impulse applied to a motor to change the speed of the mail piece while the mail piece is gripped by the weigh belts; a pair of secondary transport belts arranged for gripping a mail piece there-between as it exits the weighing station and moving the mail piece along the transport path at the predetermined transport speed; wherein the primary transport belts, and the secondary transport belts, are arranged so that none of them contacts the mail piece while the mail piece is gripped in the weighing station during a weighing operation.
 17. The in-line weighing apparatus according to claim 16 including: a capstan servo motor arranged to synchronously drive the pair of weigh belts; a servo controller coupled to the capstan servo motor to control the capstan servo motor to a predetermined command speed that is different from the transport speed; the servo controller also arranged to acquire motor torque data from the capstan servo motor as the mail piece moves through the weighing station, so that the captured torque data reflects the torque applied by the capstan servo motor to change the mail piece speed from the intake transport speed to the command speed; and a processor arranged to determine a weight of a mail piece from the captured torque data.
 18. The in-line weighing apparatus according to claim 17 and including: a first photocell positioned along the transport path for detecting when a mail piece enters the weighing station; a set of repositionable guide rollers arranged for moving the weigh belts into proximity with one another for gripping the mail piece in between them; the guide rollers arranged to reposition the weigh belts so that the mail piece is gripped between the weight belts and the secondary transport belts no longer contact the mail pieces; and a scale system controller coupled to the first photocell for detecting when a mail piece enters the weighing station, and coupled to the repositionable guide rollers for repositioning the guide rollers so as to move the weigh belts into proximity with one another for gripping the mail piece in between them responsive to a mail piece entering the weighing station.
 19. The in-line weighing apparatus according to claim 18 and including: a first memory for storing servo motor torque data acquired from the servo controller during a weighing operation; a second memory storing calibration data; and wherein the processor is coupled to the first and second memories for determining a weight of a mail piece by comparing the acquired motor torque data to the stored calibration data.
 20. The in-line weighing apparatus according to claim 19 and wherein: the processor is arranged to calculate a Fourier transform of the acquired motor torque data; the stored calibration data comprises Fourier transform coefficients; and the processor determines the weight by comparing the calculated Fourier transform of the acquired motor torque data to the stored calibration Fourier transform coefficients.
 21. The in-line weighing apparatus according to claim 19 and wherein the torque data is acquired over a measurement period of less than approximately 70 msec in order to weigh a mail piece in real time at a typical transport speed. 